Coronary heart disease (CHD) is the leading cause of death in women, accounting for 36% of all deaths (approximately 380,000 deaths per year). CHD-related mortality is greater than breast and lung cancer mortality combined. Clinical studies have shown that estrogen replacement therapy (ERT) in the postmenopausal period may reduce morbidity and mortality by 50% or more.
Estrogen deprivation is also an important cause of postmenopausal osteoporosis. Osteoporosis affects about one-third to one-half of all postmenopausal women. Annually, 500,000 vertebral fractures occur. Nearly one-third of women over age 65 will suffer at least one vertebral fracture. Estrogen replacement therapy has been determined to substantially reduce the risk of osteoporosis.
In spite of the reports of substantial reduction in the incidence of both coronary heart disease and osteoporosis associated with estrogen replacement therapy, poor compliance with such therapy has prevented a major impact on women's health overall. Studies have found that the two principal disincentives for women to continue estrogen replacement therapy are fear of breast cancer, and the adverse effects of the progestin (i.e., the nuisance of continuing menstrual periods, cyclic depression, breast tenderness and symptoms like those of premenstrual syndrome) used to prevent endometrial carcinoma. Aside from the breast cancer fear, the other disincentives all relate to the need to use a cyclic or continuous progestin (i.e., medroxyprogesterone acetate) to prevent the risk of endometrial carcinoma.